Saponification of esters of organic acids



Patented Jan. 17, 1933 I UNITED STATES PATENT OFFICE WALTER BADEROF sronnon, NEAR .DERBiLENGLAND, ASSIGNOR r CELANESE CORPORATION or AMEmcA, A COBPOBATIONOF DELANARE SAIPONIFICATION OF ESTEIRS OF ORGANIC ACIDS No Drawing. Original application July 20, 1926. Divided and this application filed. July 26, 1928.

This invention relates to the hydrolysis or saponification of esters of organic acids.

This application is a division of application S. No.-138,116filed Sept. 27, 1926 and issued as Patent No. 1,864,643 on June 28, 1,932.

i In preparing free organic acids from their esters, it has been customary to perform the saponification in the presence of an excess of water, because, the reaction being reversible, a large mass of water favours the formation of free acid. If the organic acid is insoluble in water, its separation-from the reaction mixture is easy, but in the case of the lower fatty acids which are soluble in water, the separation of the acid in concentrated form is a more diflicult and expensive operation. 1

According to this invention, the saponification of esters of organic acids, and particularly of lower fatty acids which are soluble in water, especially methyl acetate, is performed in such manner as to producethe free acids in an anhydrous or concentrated condition. For this purpose the saponification is effected by heating the said esters with a saponifying agent in the presence of just the theoretical amount of water required for the reaction, a strong mineral acid, for'example, phosphoric acid or sulphuric acid, being preferably used as saponifying agent.

In the case of methyl acetate, for example, the reaction results in the formation of acetic acid and dimethyl ether, according to the following equation:

QCILCOOH (CH3) 20 It is preferred to use phosphoric acid as saponifying agent, since it does not act as an 40 oxidizing agent at the, temperatures employed. The reaction takes place at temperatures between about 150 and about 300 C., temperatures between 180 and 220 C. being specially advantageous for the saponification of methyl acetate; For instance, at 200 C. the reaction proceeds rapidly, and results in substantially a quantitative yield of glacial acetic acid.

The more highly hydrated forms of phos- 9 phoric acid, for instance, ortho phosphoric.

filed September 27, 1926, Serial No. 138,116, and in'Great. Britain Serial Nd. 295,611.

acid and pyrophosphoric acid, are capable of supplying the water required for the saponification, being themselves at the same time dehydrated to the form of meta phosphoric acid. It is therefore possible to perform the reaction in ,a continuous manner, by continuously introducing supplies of ester and water in the requisite proportions into the phosphoric acid, the phosphoric acid serving in effect as a carrier for the water, The reaction may be carried out in any apparatus designed for the interaction of gases and liquidsffor example, wash towers, mixers, bubblers etc. i

The saponification of methyl acetate, for example, may be carried out by passing it in the form of vapour together with the requi- The following examples will illustrate this method of saponification, but]: do not restrict my invention to the particular methods hereinafter described. i

I Example 1 1 A closed copper vessel of high cylindrical shape, with a quick running agitator of the propeller type is nearly filled with phosphoric acid and kept by outside heating at 180-220 C. The vapour of methyl acetate is intro duced near the bottom of the vessel, and also the required amount of steam, while the top is connected to a condenser and receiver. The gas escaping from the receiver is pure methyl ether. The condensate is glacial acetic acid,

with more or-less unchanged methyl acetate, which is easily distilled off.

Example 2 What I claim and desire which is not substantially The saponification processes herein described can also be applied to ethyl acetate methyl'propionate, and other esters or organic acids.

to secure by Letters Patent is 1. A process for producing a concentrated organic acid, which comprises saponifying an ester thereof in the presence of an acid saponifying a ent by means of a quantity of Water not substantially greater than one molecule of water be saponified.

2. A process for lower fatty acid, which comprises saponifying an ester thereof in the presence of an acid saponifying agent by means of a quantity ofwater not substantially greater than one molecule of water for each ester group to besaponified.

3. A process for producing concentrated acetic acid, which comprises saponifying an ester thereof in the presence of an acid saponifying agent by means of a quantity of water not substantially greater than one molecule of water for each ester group to be saponified.

4. A process for producing a concentrated organic acid, which comprises heating an ester thereof with an acid saponifying agent, in the presence of a quantity'of water which is not substantially greater than one molecule for each ester group to of water foreach ester group to be saponified.. r

5. A process for producing concentrated acetic acid, which comprises heating an ester thereof with an acid saponifying agent in the presence of aquantity of water which is not substantially greater than one molecule of water for each ester group to besaponified.

6. A process for producing a concentrated organic acid in the free state, which comprises heating an ester thereof with a strong mineral acid in the presence of a quantity of water which isnot substantially greater than one molecule of water for each ester groupto be saponified.

7. A process for producing a concentrated organic acid in the free state, which comprises heating an ester thereof with a phosphoric acid in the presence'of a quantity of water whichis not substantially greater than one molecule of water for each ester group to be saponified.

8. A process for producing a concentrated lower fatty acid in the free state, which comprises heating an ester thereof with a strong mineral acid in the presence of a quantity of water which is not substantially greater than one molecule of water for each ester group to be saponified.

9. A process for producing concentrated acetic acid in the free state, which comprises heating an ester thereof with a phosphoric acid in the presence of a quantity ofwater greater thanv one producing a concentrated molecule of water for each ester saponified. I

10. A process forisaponifyingan ester of an organic acid, which comprises splitting it into the corresponding ether and acid by means of an acid saponifying agent and substantially the quantity of water which is theoretically necessary for the production of the ether and the anhydrous acid.

11.. A process for saponifying an ester of it into the corresponding ether and acid by means of an acid saponifyingagent and substantially the quantity of water which is'theoretically necessary for the production of the ether and the anhydrous acid.

group to be V a lower fatty acid, which comprises splitting 12. A process for saponifying methyl ace- A ence of a strong mineral acid by means of substantially the quantity of water which is theoretically necessary forthe productionof the ether and the anhydrous acid, and simultaneously vaporizing at least one of the products of saponification.

. 14. A process for 'saponifying an ester for the production of a lower fatty acid and an ether, one at least of said products being volatile attemperatures below 300C which comprises saponifying the ester in the pres ence of phosphoric acid by means of substantially the quantity of water which is theoretically necessary for the production of the ether and the anhydrous acid, and simultan eously vaporizing at least one of the products of saponification. c

15. A process for the production of dl: methyl ether and acetic acid, which comprises saponifying methyl. acetate in the presence'of phosphoric acid by means of substantially the quantity of water which is theoretically necessary for the production of dimethyl ether and anhydrous acetic acid, and simultaneously vaporizing the products of saponificat-ion. t

.16. A process for saponifying an ester'of an organic acid, which comprises heating the ester with a phosphoric acid in which the ratio of water to phosphoric oxide 1s greater than that in metaphosphoric acid, separating the products of saponification from the de-.

hydrated phosphoric acid, and re-hydrating the phosphoric acid for reuse in the saponification process. o

process for producing 17. A dimethyl ether and concentrated acetic acid, which comprises heating methyl acetate with a phosphoric acid in which the ratio of water to phosphoric oxide is greater than that in metaphosphoric acid, separating the products of saponification from the dehydrated phosphoric acid, and re-hydrating the phosphoric acid for re-use in the saponification process.

18. A process for saponifying methyl acetate, which comprises bringing its Vapour into contact with phosphoric acid maintained at 180 -220 (1., in the presence of substantially the quantity of steam theoretically necessary to convert the methyl acetate into dimethyl ether and acetic acid.

19. A process for saponifylng methyl acetate, which comprises passing its vapour in counter-current in contact with phosphoric acid at 180-220 (l, the phosphoric acid being circulated and maintained in a hydrated form'by means of substantially the quantity of the production of dimethyl ether and acetic acid.

20. A process for saponifying an ester of an organic acid, which comprises heating the ester with at least one of the more highly hydrated forms of phosphoric acid.

21. A process for saponifying an ester of a lower fatty acid, which comprises heating the ester with ortho phosphoric acid.

In testimony whereof I have hereunto subscribed my name.

WALTERBADER.

steam theoretically requisite 'for' 

